The present invention relates generally to communications using radio wave antennas, and relates more particularly to antennas for transmitting and receiving at a higher range of frequencies and a discrete lower range of frequencies.
A dual-band antenna, as its name implies, covers two separate or discrete frequency bands, thus allowing it to replace two single-band antennas. Due in large part to stricter zoning requirements, there is a growing need for dual-band base-station antennas. The advantages of reducing the number of antennas needed at a base-station site include reduced xe2x80x9cvisual pollutionxe2x80x9d, weight, wind-loading, and installation costs, as well as easier zoning approval. In addition, even if a carrier currently only uses one band, it can install a dual-band antenna now and reserve the unused band for future use. This reduces the expense of installing new antennas in the future and the trouble of having the site re-approved by a zoning board.
The present application is directed to particular features of a dual-band antenna. One aspect of the invention includes a ground plane, at least one array of individual low-frequency antenna elements disposed linearly along the ground plane and at least one array of individual high-frequency antenna elements.
In certain embodiments of the present invention, the array of high-frequency elements is elevated above the at least one of the low-frequency elements. The array of high-frequency elements may be asymmetric about its center.
In further embodiments, the arrays of low-frequency elements may be symmetrical about their centers, and individual low-frequency elements in separate arrays may be vertically aligned.
In still further embodiments, a high-frequency beamforming rod is disposed between the array of low-frequency elements and the array of high-frequency elements.
The low-frequency elements may include a gusset for securing one of the individual low-frequency elements to the ground plane. The gusset may further include a notch or the like for supporting at least a portion of the high-frequency beamforming rod.
The array of high-frequency elements and the beamforming rod cooperatively form a symmetrical azimuth radiation pattern in a high-frequency band, and the at least one array of low-frequency elements form a symmetrical azimuth radiation pattern in a lower-frequency band.